Generator vs. battery backup: which fits your home?

Both keep the lights on when the grid goes down, but they solve the problem differently. A generator makes electricity from fuel. A battery stores electricity and gives it back. That one difference drives almost every trade-off below. This guide compares them honestly, with no brand pitch, so you can decide which questions to ask. Our generator and backup power page covers the installation work we do.

Two numbers that decide it: power and energy

Power is how much can run at the same moment. Energy is how long it can keep running. A generator's power is set by its size, and its energy is limited only by fuel. A battery has a power rating, which limits how many things can run at once, and a fixed amount of stored energy, which runs down as you use it.

That's why the two feel so different in a long outage. A generator on a steady fuel supply will still be running on day three. A battery will last as long as its stored energy and your usage allow, unless something, like solar panels, recharges it.

Starting surges: where batteries can struggle

Motors and compressors, like well pumps, sump pumps, air conditioners and heat pumps, draw a burst of power when they start, well above their running load. A generator has to absorb that surge, and so does a battery's inverter. If your must-run list includes a deep well pump or central air, check that the system you're considering can start it, not just run it. Our guide to sizing a whole-home generator explains how running and starting loads add up.

Noise, exhaust and placement

A generator burns fuel, so it makes noise and exhaust and has to sit outside, away from doors and windows. The U.S. Consumer Product Safety Commission calls portable generators one of the leading causes of carbon monoxide deaths after storms, and says to run them outdoors only, at least 20 feet from homes and buildings, never in a garage, basement, crawlspace or shed. A battery makes no exhaust and runs quietly, which is a real advantage in a tight lot or a rowhome with no yard.

Upkeep

A standby generator is an engine. It needs periodic exercise runs, oil and filter changes, and a fuel supply you can count on. A battery has far fewer moving parts. Either way, the transfer equipment and the connection to your panel should be checked from time to time.

Both follow the electrical code

The National Electrical Code has rules for both: optional standby systems and generators on one side, energy storage systems on the other. Either way, the connection to your home's wiring is permitted and inspected electrical work in Harford County, Baltimore County and Baltimore City, and both have to keep backup power from feeding back into the utility lines, which protects line workers.

When a generator is the better fit

• Outages that can run for days, such as after a major storm
• A deep well pump, central air or electric heat on the must-run list
• You want the whole house running as normal
• Room outside to place a unit away from doors and windows

When a battery can make sense

• Outages that are usually short
• A modest must-run list: fridge, lights, internet, a few outlets
• Solar panels that can recharge it during a long outage
• No good outdoor spot for an engine, or noise and exhaust rules it out

Start with your must-run list

The fastest way to narrow the choice is to write down what has to keep running, and for how long. A typical list might look like this:

• Heat: the furnace blower or boiler controls, or a heat pump
• Water: a well pump, and a sump pump if the basement takes on water
• Food: the refrigerator and any freezer
• Health: medical equipment that needs power
• Basics: some lights, phone charging, internet and a few outlets

If the list is short and the outages you remember lasted hours, not days, a battery may cover it. If the list includes a well pump, central air or electric heat, or you've sat through multi-day outages, a generator is usually the more practical answer.

Write down how long your last few outages lasted, too. That single number, hours or days, does more to settle the generator-or-battery question than any spec sheet, because it tells you whether stored energy would have been enough.

Questions to ask any backup power installer

1. What loads will this system run at the same time, and can it start my largest motor?
2. How will it connect to my panel, and does my panel need work first?
3. Is the switchover automatic or manual, and what happens when utility power returns?
4. Who pulls the electrical permit, and when is the inspection?
5. What maintenance does it need, and who does it?

Or a combination

Some homes use both: a battery for short blips and quiet nights, and a generator for long outages. It adds equipment and cost, so it's worth it mainly when both outage lengths are a real problem for your house.

The common starting point

Whichever way you lean, the first steps are the same: list what has to run, measure what the house actually draws, and look at the panel. An older or full panel may need work before any backup system connects to it; see panel and service upgrades. Wyatt Electric has done electrical work in Harford County, Baltimore County and Baltimore City since 1986. We'll look at your panel and loads, explain the options and give you a price before anything starts.